For a stab trim runaway, what action should be taken?

For a stab trim runaway, what action should be taken?

• A. MASTER DISCONNECT...Press and Hold
• B. Adjust trim manually
• C. Re-engage trim opposite direction
• D. Cut power to elevator actuators

Answer: (A)

When stab trim starts moving on its own, the priority is to stop the trim system quickly. The reliable way to do that is to remove power from the trim actuators by using the Master Disconnect switch and holding it until the trim motion ceases. This takes the load off the control surfaces and lets you regain manual control safely. Manual trim adjustment won’t fix a runaway and can make control inputs worse or cause damage. Re-engaging trim in the opposite direction could intensify the runaway. Cutting power only to the elevator actuators isn’t the standard method to arrest a stab trim runaway, since you want to isolate the entire trim system. So, pressing and holding the Master Disconnect to cut power is the correct action.

When stab trim starts moving on its own, the priority is to stop the trim system quickly. The reliable way to do that is to remove power from the trim actuators by using the Master Disconnect switch and holding it until the trim motion ceases. This takes the load off the control surfaces and lets you regain manual control safely.

Manual trim adjustment won’t fix a runaway and can make control inputs worse or cause damage. Re-engaging trim in the opposite direction could intensify the runaway. Cutting power only to the elevator actuators isn’t the standard method to arrest a stab trim runaway, since you want to isolate the entire trim system. So, pressing and holding the Master Disconnect to cut power is the correct action.